This invention relates in general to data communication, and more particularly to a communication server apparatus and method.
A communication server provides access to communication facilities. For example., a communication server having a bank of modems may provide subscriber access to the modems for data communication. A communication server may be associated with its own dedicated communication network, or with an existing communication network, such as the public switched telephone network (PSTN).
As communication networks provide greater connectivity and access to information, there is an increasing demand for data communication at higher rates. One solution to provide increased data rates replaces existing twisted pair wiring with high bandwidth media, such as coaxial cables or fiber optic links. Other solutions adopt improved communication techniques using the existing hardware infrastructure. For example, digital subscriber line (XDSL) technology provides higher bandwidth data service over existing twisted pair wiring.
To deliver data service to the subscriber, a communication server may provide a dedicated or permanent connection to its communication facilities. For example, an existing communication server at a central office provides enough communication facilities to simultaneously service all PSTN subscribers. However, all telephone subscribers may not desire data service. Furthermore, the subscribers that desire data service may not simultaneously access the communication server.
In accordance with the present invention, the disadvantages and problems associated with communication servers have been substantially reduced or eliminated. In particular, a communication server apparatus and method are disclosed that provide data service using profile information for twisted pair lines in an XDSL environment.
According to one aspect of the present invention, a communication server coupled to a number of twisted pair lines includes a number of XDSL transceiver units. A line profile table has profile information for the twisted pair lines. A system controller receives profile information for a twisted pair line from the line profile table and provides the retrieved profile information to an XDSL transceiver unit coupled to the twisted pair line in preparation for XDSL communication.
In accordance with another aspect of the present invention, an XDSL transceiver unit includes an XDSL chipset that couples to a twisted pair line and a number of registers associated with the XDSL chipset. A microcontroller coupled to the XDSL chipset and the registers receives profile information for the twisted pair line from an external device and stores the profile information in the registers in preparation for XDSL communication using the twisted pair line.
Important technical advantages of the present invention include a communication server that provides data service to a number of subscribers using a reduced number of XDSL communication facilities. Over-subscription of data service is accomplished by selectively coupling a number of twisted pair data lines to a reduced number of XDSL modems. A controller polls the data lines simultaneously or in succession, in groups or individually, to determine which subscribers of the communication system need data service. Upon detecting a need for data service on a selected data line, the controller directs a switch to couple the selected data line to an available modem. The communication server may then provide data service suitable for high bandwidth applications, such as video-on-demand, multimedia, or Internet access.
Another important technical advantage of the present invention includes a communication server that provides over-subscribed XDSL data service using the existing infrastructure of the public switched telephone network (PSTN). Asymmetric digital subscriber line (ADSL), symmetric digital subscriber line (SDSL), high-speed digital subscriber line (HDSL), very high-speed digital subscriber line (VDSL), or other suitable XDSL technology can provide higher bandwidth data service over existing twisted pair wiring. These technologies may support data service simultaneously with traditional telephone service using a separation technique, such as frequency division multiplexing. In one embodiment, a splitter divides each incoming twisted pair subscriber line into a twisted pair phone line and a twisted pair data line. The phone line is coupled to a telephone switch to provide telephone service and the data line is coupled to the communication server to provide over-subscribed XDSL data service. The communication server and splitter may be located at a central office, remote terminal, or other point of presence of the data service provider.
Another important technical advantage of the present invention includes the management and monitoring of XDSL data service provided to subscribers. To accomplish this, the communication server maintains an activity table to determine status information on twisted pair data lines and XDSL modems. In addition, the communication server can track subscriber usage, monitor subscriber information and generate billing and demographic information. In a particular embodiment, an activity detector disconnects a subscriber after a predetermined period of inactivity to release a modem for use by another subscriber.
An important technical advantage of the present invention is the distribution of the switching function to allow scalability of the number of supported data lines and over-subscription of XDSL modems.
A further important technical advantage of the present invention includes isolating the switch from the data lines and subscriber lines. The switch can thereby operate without constraints imposed by technical requirements for interaction with the data lines and subscriber lines. For example, isolation of the switching matrix can allow CMOS switches to be used rather than more expensive solid state relays or mechanical relays.
Yet another important technical advantage of the present invention includes the ability to provide a two-wire isolated interface that can use a single switch to couple a data line to a specific modem. The present invention thus allows one switch per modem per data line configuration. The isolation system of the present invention can transform the data line impedance to an intermediate impedance in order to increase system performance.
A further important technical advantage of the present invention includes the maintenance of profile information for one or more twisted pair lines coupled to an XDSL transceiver unit. This profile information may specify filter coefficients, equalizer tap values, sub-band weighting, data rates, margins, and other information that reflects electrical and/or physical parameters of the twisted pair lines. In a particular embodiment, the XDSL transceiver unit performs a training session on the twisted pair line at a variety of bands and rates to generate profile information. The profile information is stored in an appropriate non-volatile memory, such as a memory maintained by the system controller or other device external to the XDSL transceiver unit. The XDSL transceiver unit receives the stored profile information to engage in XDSL communication without a protracted training period. The XDSL transceiver unit may also perform a full or partial retraining of the line as needed.
The profile information may include, for example, digital filter coefficients used in carrier-less amplitude phase (CAP) modulation, discrete multi-tone (DMT) modulation, or other suitable modulation. In a particular embodiment, a communication server includes a number of XDSL transceiver units arranged on cards that communicate with one or more system controller cards to receive profile information of associated twisted pair lines serviced by the communication server. Line interface modules (LIMs) couple the twisted pair lines to selected XDSL transceiver units under the control of the system controller. In this embodiment, the system controller maintains profile information associated with each twisted pair line serviced by the communication server. Other important technical advantages are readily apparent to one skilled in the art from the following figures, descriptions, and claims.